The improved orbital automatic voltage control weld head tool of the invention is particularly adapted for use in the field of service and maintenance of steam generators and, specifically, steam generators of nuclear steam supply systems.
Automatic arc welding tools are known which create movement in response to arc current or voltage, as mentioned in U.S. Pat. No. 4,575,612. Circular path orbiting weld heads with ceramic or insulative sheathing, inert gas shielding and a tungsten weld tip are known for use when fixed in position on a workpiece, see, for example, U.S. Pat. Nos. 3,084,243; 3,350,537; 3,740,520; 4,580,028 and Canadian Pat. No. 715,679, issued Aug. 10, 1965, a copy of which is in the examiner's art collection in the U.S. Patent and Trademark Office at 219/60.2.
In any rotary or orbital weld head structure, it is important to pass the welding current or voltage from a relatively fixed structure to a rotating structure. U.S. Pat. Nos. 3,132,421; 3,395,263; 3,740,520; 3,701,072 and 3,784,782 have been cited as pertinent to patentability and this problem in the aforementioned Ser. No. 28,997 of the inventor. Also mentioned in that application, for these reasons, is Soviet Union Document No. 574,800 dated Sept. 1977, a copy of which is in the examiner's art collection in the U.S. Patent and Trademark Office at 439/17. U.S. Pat. No. 3,784,782 also provides a current path from fixed to rotating members.
Despite the existence of the noted prior endeavors in the art, there has been a need for an improved compact tool for use in orbital automatic voltage control welding of nozzle dam inserts, steam generator tube plugs, tube sheet plugs, sleeve plugs and sleeve welds. This need is especially great for a tool which can conveniently operated from the end of a manipulator arm of the type used below steam generator tube sheets in nuclear steam supply systems.
A primary goal in producing maintenance and service tools, including orbital weld heads for use in nuclear steam supply system components, is to provide a tool which eliminates or minimizes the exposure time to radioactivity of the service personnel. The improved orbital weld head, when mounted on a manipulator arm, accomplishes one hundred percent (100%) tube sheet coverage and is very versatile.